2002 Chevy Bose Aux Jack Install


I recently purchased a 2002 Chevy Express 1500 LT Van.  This comes with the full boat sound system from the era, including a 6 disc CD changer and a Video Cassette player with a couple of fold down LCD screens and wireless headphones.  Very cool, sounds quite nice - but it has one problem: no Aux input for my MP3 player.  I figured Crutchfield would take care of me, but once I put "Bose" in the system picker, it said "Tilt" (nothing available).

I tried a Scosche FM Modulator - it sounded like CRAP.  The one I had laying around that plugs into the cigarette lighter worked slightly better mainly because I could continually search for an unused frequency while traveling cross country.

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I found several things on the internet.

Owners manual PDF: download here 

That was no help - didn't really document the sound system at all.

I found wiring diagrams for the sound system, showing why Crutchfield doesn't offer replacement head units.  It's 4 separate pages, each in its own PDF file:

Download here, here, here, and here.  The first of these 4 shows the connections coming out of the back of the radio going to the Amps.  These are the ones we'll use.

I found an intriguing post on the internet where someone says you can tap into the wiring harness and send an alternate signal to the amplifiers.  Here's the post: 

2002 Trailblazer / GMC Envoy Owners 


Just a note to those who have the Class II RDS w/Bose and 6-disc in-dash radios (model #15058231): Apparently, no one make an AUX-IN kit that works correctly with this particular unit. I talked to an engineer at PAC-AUDIO and at USA-SPEC, they both said the radio has the aux disabled because it uses it for the built in 6-disc.

But there is a work around: The head unit sends its audio to the amps at a constant level, and the amp's volume is digitally controller via the Databus. So you can do this: Wire up a relay switch to toggle between your own input and the radio's output.

24-pin connector:
A9 - Left (-) dk green
A8 - Left (+) tan
B10 - Right (-) org / blk
B11 - Right (+) lt green

You MUST use a ground loop isolator and 2 DPDT relays so that you are completely disconnecting all 4 wires from the head unit and connecting them to your own input. 

Radio Left (-) ----------/------- Amp Left (-)
Radio Left (+) ----------|/------ Amp Left (+)
Radio Right (-) ---------||/----- Amp Right (-)
Radio Right (+) ---------|||/---- Amp Right (+)

In L (-) --------|************| --- To Amp L (-)
In L (+) --------|GND Isolator| --- To Amp L (+)
In R (-) --------|************| --- To Amp R (-)
In R (+) --------|************| --- To Amp R (+)

I tried it out and it works great! It's a little tight to splice the factory harness, but it does the trick.


This was the basis for my conversion.  The instructions above only handle the front two channels, however.  I doubled up on relays and ground isolators and used RCA splitters to send the signal from the MP3 player to both the front and rear channels.  I also found that the output of the MP3 player wasn't high enough to get the volume I wanted, so I used a "Boostaroo" headphone amplifier from Radio Shack to boost the signal.  This one is battery operated.  I also bought a 12v powered unit from Boostaroo directly, but the cigarette light induced too much background noise so I'm back to the battery operated one.  The 2 AA batteries last a surprisingly long time.

I had previously installed an on/off switch and headphone jack to RCA splitter / adapter that came with the Scosche FM adapter.  Additional items I purchased to make this conversion:

Radio Shack 270-054 ground loop isolator - Qty 2 (came with RCA to headphone adapters which I used to connect the RCA jacks to the relays)

Radio Shack 275-218 DPDT relay - Qty 4

Radio Shack 274-511 RCA splitter / Y adapter - Qty 2

Heat Shrink tubing

"Small" (0.164"?) Female spade connectors - worked great on the relay's terminals

Radio Shack 33-118 Boostaroo Headphone Amplifier

Here's the basic wiring:

Connections we're going to splice into:

LF LO Aud Sig + A8 Tan/Blk
LF LO Aud Sig - A9 Dk Grn
RR LO Aud Sig - A10 Tan
RR LO Aud Sig + A11 Dk Blu
LR LO Aud Sig + B8 Brn
LR LO Aud Sig - B9 Brn/Wht
RF LO Aud Sig - B10 Lt Grn/Blk
RF LO Aud Sig + B11 Lt Grn

Each one of these connections gets turned into this:

Radio ---------------------------------------- Relay (normally closed)
MP3 headphone ----- Ground Loop Isolator ----- Relay (normally opened)
Amp ------------------------------------------ Relay (common)
Power (on/off switch in positive lead) ------- Relay

The MP3 connection is simplified above. Here's the full series of connectors:

MP3 headphone --- RCA Adaptor --- Ground Loop Isolator --- RCA Adaptor --- Relay

Each relay can handle both a (+) and a (-) connection.

The power connections from the switch and the ground can be connected to the relays in series (jumpered)

With the Radio Shack 275-218 DPDT relay, the amp connection is closest to the power connections, 
the MP3 player connections are next, and the radio connections are furthest from the power connectors.

Here's a pictorial view of this installation:

Note: click on the pictures for a larger view


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Pre-existing connections from prior installation - front / back

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Radio removal

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Splicing into wiring harness - note that each channel's wires are twisted around each other to reduce noise - there are 2 twisted bundles of 4 wires each.  This helps finding the right wires.

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The RCA connectors with the spade connectors soldered to them - be careful as there are TWO small wires in addition to the outer shield.  One of the small wires is connected to the outer shield / ground and the other is connected to the positive inner terminal.  I soldered both wires into a couple of my connectors the first time around and only had 2 of the 4 channels working until I re-did them.

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Here's how to do the splice - first wrap both wires around each other for strength, then solder together, then cover with heat shrink tubing

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Twist the wires together to gain the noise reduction of "twisted pair" like the stock wiring harness

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Notice that all of the wires are labeled.

Here's the power connections on all 4 relays (jumper the + terminals together, jumper the - terminals together)

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Here I have the amp connections as well as the RCA jack (MP3 player) connectors attached.  Note the electrical tape strain relief - I taped the RCA jacks to to the amplifier wires so the thin little wires aren't pulled off of the connectors.

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Here's the full set of connections on the relay.

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What I don't show is the RCA jacks from the dashboard headphone jack connected to a Y adaptor and then to the Ground Loop Isolators.  The relay's RCA jacks connect to the other side of the Ground Loop Isolators.  I re-installed the radio and stuffed the 4 relays and the two ground loop isolators in the space under the radio.  Pretty much a net fit, but here's the end result (yes, that is a brown 30 GB Zune - so geeky I HAD to have that one)

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